JPS59124552A - Copying control device - Google Patents

Abstract

PURPOSE:To reduce cutter bite at a rapidly changing point of a model shape while enabling said point to be detected in an early stage by changing a reference value based on the amount of changes per unit time of a displacement signal from a tracer head for tracing a model surface. CONSTITUTION:Displacement signals epsilonx-epsilonz from a tracer head 1 is sampled in a sampling circuit 2 at every prescribed time, and a copying operation is performed in a copying arithmetic circuit 3 on the basis of said sampled vaues. And, a motor 5 is driven and controlled by an output from said circuit 3, and the tracer head 1 and a model 4 are relatively moved, allowing copying control to be performed. Here, the amount of changes per unit time of a displacement signal is estimated by a change amount detecting means 6 based on the above described sampled values, and a reference value is set by a reference value setting means 7 based on said amount of changes. And, when the difference, evaluated in a control means 8, between the above described amount of change and its reference value is more than prescribed value, the relative speed between both 1, 4 is controlled to be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an improvement in a tracing control device that samples displacement signals corresponding to a model shape output from a tracer head and performs tracing control based on the sampled values. The present invention relates to a tracing control device capable of reducing the biting of a cutter at a sudden change point J2 of a model shape.

Prior Art and Problems As the speed of microprocessors increases, it has been proposed to construct a tracing control device that requires high-speed followability using a microprocessor instead of a conventional analog circuit.

By the way, when copying a model M having a shape as shown in FIG. 1, a phenomenon occurs in which the cutter bites into the workpiece at a sudden change point in the model shape, such as a corner P.

In order to reduce the biting of the cutter at such sudden points of change in the model shape, an analog type copying control device takes the following steps, for example.

In other words, it changes suddenly at the sudden change point of the composite displacement signal model shape which is a composite of the X, Y, and Z axis displacement signals εX, εr, and ε2 output from the tracer head, and the unit of the composite displacement signal is The amount of change dε τ per time also increases rapidly at sudden points of change in the model shape, such as the corner P, as shown in Figure 3. Therefore, by comparing the change meter and the threshold value, When the amount exceeds a threshold value, the feed speed is decelerated to reduce the biting of the cutter. In addition to this, the composite displacement signal ε,
Find the amount of change per unit time in the displacement signals εX, εY, and ε2 of each axis, compare each amount of change with the threshold corresponding to each amount of change,
There is also a device in which deceleration control is performed when at least one of the amounts of change exceeds a threshold value.

However, in order to reduce cutter biting in a digital scanning control device using a microprocessor, the method used in the analog scanning control device described above could be applied as is. There are some drawbacks. That is, since the digital scanning control device samples the displacement signals εX, εY, and εZ from the tracer head at regular intervals, the amount of change π of the composite displacement signal ε per unit time is as shown in FIG. As shown in , even if it exceeds the threshold value, it cannot be detected that the amount of change m exceeds the threshold value until the numbering time t+1 dε is reached.
There was a drawback that the cutter had a large amount of biting.

In order to improve this kind of defect, it is possible to lower the threshold level, but if the threshold level is lowered, the model shape may be affected if the model surface is rough and the amount of change in the composite displacement signal εdε is large. There is a risk that points other than the sudden change point of the model shape may be detected as the sudden change point of the model shape. Conversely, even if the Moda/1 surface is rough, the threshold value should be set to a high level in order to prevent points other than the sudden change point of the model shape from being detected as the sudden change point of the model shape. It was necessary to leave it there.

Purpose of the Invention The present invention has been made to improve the above-mentioned drawbacks.The purpose of the present invention is to perform scanning control based on sampling values of displacement signals, and to use a digital scanning control device to detect sudden changes in the model shape. The objective is to reduce the biting of the cutter.

Structure of the Invention As shown in FIG. Perform copy calculation using
The output of the tracing calculation circuit B drives the motor 5 that moves the tracer head 1 and the model 4 relatively, and generates a composite displacement signal ε and a reference displacement signal ε. In a tracing control device that relatively moves a trainer head 1 and a model 4 so that the difference between The amount of change in the hit is determined, and the amount of change detection means 6 is determined by the reference value setting means 7.
A reference value is set based on the detection result of the tracer head 1 and the model 4, and the control means 8 compares the reference value with the detection result of the change amount detection means 6. If the difference between the two is more than a certain value, This is to reduce the relative feed speed.

Embodiment of the Invention FIG. 5 is a block diagram of an embodiment of the present invention, in which 10 is a processing device including a microprocessor, 11 is a memory, 12 is a tracer head, 13 is an AD converter, and 14 is a data input device. , 15 is a data output device.

16 is a DA converter, 17 is a drive circuit, and 18 is a motor for relatively moving the tracer rad 1 and a model (not shown). Incidentally, there are actually six motors, and each motor moves the stylus 12 and the model in X, Y,
This is a relative movement in the axial direction, but here X
Only the axial motor 8 is shown.

X, Y, and Z displacement signals gz from the tracer head 12.

εY and ε2 are applied to the processing device 10 via the report converter 13 and the data input device 14. The processing device 10 receives displacement signals εX, εY applied via a data input device 14.

εZ is sampled at regular intervals of ζ, a tracing calculation is performed based on the sample value, and the calculation result is sent to the data output device 1.
5 to the DA converter 16. The DA converter 16 converts the digital signal from the data output device 15 into an analog signal and applies it to the drive circuit 17, and relative transmission between the drive circuit and the model is performed.

In addition to the above-described tracing control, the processing device 10 also performs the following processing in order to reduce the biting of the cutter at sudden points of change in the model shape.

For example, if we follow the model M shown in Figure 1 with the X-axis as the feed axis, the displacement signal εX in the X-axis direction and the amount of change per unit time of the displacement signal εX are shown in Figure 6 (A
) l CB>. When copying processing is started, the processing device 10 calculates the amount of change in the sampling value, that is, the change per unit time in the displacement signal εX, based on the current chimbling value S3 of the displacement signal εX and the previous sampling value 5n-1. Find the quantity DrL and find its absolute value I Dn l
is stored in the memory 11 as a reference value. Next, when the processing device 10 detects a new sampling value SrL+1,
Based on this sampling value 5n4-1 and the previous sampling value S, the amount of change DrL+1 is determined. Next, the processing device 1o outputs the absolute value IDrL+1 of this amount of change DTL+1.
1 and the amount of change D stored in the memory 11 as a reference value.
The absolute value IDtL+ of rL is compared, and the following processing is performed based on the comparison result.

The comparison result is 1DrLl < IDn+11 <N”
If 1Dtbl (A' is a positive number), is it the absolute value ID of the current amount of change? L++I is the absolute value of the previous change amount I
It is stored in the memory 11 in place of Dn I and is used as a new reference value.

Further, if the comparison result is ID1L+11≧#-IDrLl, the processing device 10 determines that cutter biting has occurred, and reduces the feed speed. Also, at this time, the processing device 1
If it is 0, the reference value is not rewritten.

Also, if the comparison result is IDyu+11≦1DtLl,
The processing device 10 does not perform the process of rewriting the reference value.

Thereafter, each time the processing device 10 calculates a new amount of change, it compares the absolute value of the new amount of change with the absolute value of the amount of change stored as a reference value in the memory 11, and based on the comparison result, Perform the same processing as above.

In this way, in this embodiment, the reference value is changed based on the absolute value of the amount of change in the sample value, that is, the absolute value of the amount of change in the displacement signal per unit time. Compared to the two, there are the following advantages: In other words, in the conventional example in which the reference value is set at a constant level, as mentioned above, when the model surface is rough and the amount of change in the displacement signal per unit time is large (also in cases other than sudden changes in the model shape) In order to avoid erroneously detecting the point as a sudden change point in the model shape, it is necessary to set the reference value level high, and for this reason, the detection of the sudden change point in the model shape is delayed.
There was a drawback that the bite was large.

In contrast, in this embodiment, the reference value is changed based on the amount of change in the displacement signal per unit time.
When the model surface is smooth, the reference value is small, so sudden changes in the model shape can be detected earlier than in the conventional case where the reference value was kept constant. The biting of the cutter at the sudden change point can be reduced.

Incidentally, in the embodiment, gouge is detected based on the amount of change per unit time in the X-axis displacement signal εX, but gouge is detected based on the amount of change in the composite displacement signal ε. Of course, it is also possible to do so. Furthermore, displacement signals εX, εr of each axis.

Biting may be detected based on each amount of change in the ε2 composite displacement signal ε, and deceleration control may be performed when biting is detected based on at least one of the amounts of change. Of course.

As described in detail, the present invention changes the reference value based on the amount of change per unit time of the displacement signal, so compared to the conventional example in which the reference value is kept at a constant level. This has the advantage of being able to detect sudden points of change in the model shape at an early stage, thereby reducing the biting of the cutter at the point of sudden change in the model shape.

[Brief explanation of drawings]

Figure 1 shows the model shape, Figure 2 shows the composite displacement signal ε
The waveform diagram of @6 is a diagram showing the amount of change in the composite displacement signal ε,
FIG. 4 is a block diagram showing the configuration of the present invention, FIG. 5 is a block diagram of an embodiment of the present invention, and FIG. 6 (A), CE
) are diagrams showing the waveform diagram of the displacement signal εX and the amount of change in the displacement signal gz, respectively. 1.12 is the tracer head, 2 is the sampling circuit, 3
is a copy calculation circuit, 4. M is the model, 5゜18 is the motor,
6 is a change detection means, 7 is a reference value setting means, 8 is a control means, 10 is a processing device, 11 is a memory, 13 is an AD converter, 14 is a data input device, 15 is a data output device, 16
is a DA converter, and 17 is a drive circuit. Patent applicant Fanuc Co., Ltd. Agent Patent attorney Gobe Tamamushi (3 others) Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In a tracing control device that samples a displacement signal from a tracer head that tracks a model surface at regular intervals and performs tracing control based on the sampling value, the displacement signal per unit time is calculated based on the sampling value. a change amount detection means for detecting a change amount; a reference value setting means for setting a reference value based on a detection result of the change amount detection means;
A copying control device comprising: a control means for decelerating the feed speed when the difference between the reference value set by the reference value setting means and the detection result of the change amount detection means exceeds a certain value. .